1. Field of the Invention
This invention relates to methods and apparatuses for electro-coagulation printing in which electrodes are electrified to partially coagulate conductive ink films to form ink dots on surfaces of rotation drums, from which the ink dots are transferred onto papers. This invention also relates to electrode control units used for controlling the electrodes.
This application is based on Patent Application No. Hei 11-199583 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
Recently, engineers develop electro-coagulation-type printers (hereinafter, referred to as electro-coagulation printers) using conductive ink, which operate as follows:
Conductive ink films are formed on surfaces of rotation drums, which are made of metal materials. Applying electricity between the electrodes and rotation drums, conductive ink films are partially coagulated to form ink dots on the surfaces of the rotation drums, from which the ink dots are transferred onto papers to form desired print patterns (e.g., images and characters).
For example, Japanese Unexamined Patent Publication No. Hei 11-91158 discloses a fine pitch electrode unit used for the electro-coagulation printer, which will be described with reference to FIGS. 37A to 37C. FIG. 37A shows essential parts of the electro-coagulation printer. FIG. 37B shows an example of ink dots being coagulated by applying electricity to electrodes. FIG. 37C shows an configuration of the fine pitch electrode unit containing LSI chips (or LSI circuits).
In general, the electro-coagulation printers correspond to a direct print system which does not require a printing plate. So, the electro-coagulation printers have an advantage in that a number of prints can be made uniformly and clearly at a high speed. As shown in FIG. 37B, electrified coagulation is effected on each of ink dots being arranged on a surface of a rotation drum 201 by applying electricity to electrodes of a fine pitch electrode unit 101. Due to electricity being applied to prescribed electrodes which are aligned in proximity to the rotation drum 201, ink dots are adequately condensed and solidified, while ink corresponding to other electrodes which are not electrified remain without being condensed and solidified. Then, image revealing is effected to remove the ink which is not condensed and solidified, so that an image is formed by solidified ink dots, which are transferred onto a paper (or papers). Thus, it is possible to perform high-speed printing. Because the electro-coagulation printer performs printing using ink without using the printing plate and without using photosensitive members and toner, it is possible to reduce printing cost per one sheet of print.
The fine pitch electrode unit 101 has a number of electrodes 101a to effect electrified coagulation with respect to ink dots. As shown in FIG. 37B, each of the electrodes 101a has a cylindrical shape whose diameter is xe2x80x9cdxe2x80x9d, while the electrodes 101a are arranged to adjoin each other with a prescribed pitch xe2x80x9cSxe2x80x9d. Herein, both the diameter d and the pitch S are designed to have fine dimensions which are units of micro-meters (xcexcm).
FIG. 37C shows an outline of the fine pitch electrode unit 101. The fine pitch electrode unit 101 is equipped with a fine pitch electrode section 140A including a prescribed number of fine electrodes 101a, which are aligned in a single line on a same plane and which are bared or exposed. A printed-circuit board 141 has the fine pitch electrode section 140a as one terminal end thereof. Electrode drive circuits 142 which are LSI chips or else are mounted on the printed-circuit board 141. The printed-circuit board 141 is also equipped with connectors 143 for inputting drive commands given from the external (e.g., external system or device) with respect to the electrode drive circuits 142. Printed wiring lines are laid on the printed-circuit board 141 and interconnect the aforementioned parts and components to enable operations independently. The fine pitch electrode unit shown in FIG. 37C is designed to collectively drive the prescribed number of electrodes.
Next, an example of an electrode driving method will be described with reference to FIGS. 38A to 38C. FIG. 38A shows that thirty-two electrodes are switched over and driven respectively. Herein, every thirty-two electrodes are grouped in connection with a full print width of a dot-matrix format, for example. The thirty-two electrodes are supplied with a pulse signal (see FIG. 38B) consisting of pulses whose pulse widths represent gradation values. Herein, every single electrode within the thirty-two electrodes is designated by a switch 145 and is driven according to needs. The fine pitch electrode unit as a whole includes input lines, a number of which is calculated by N÷32 (where xe2x80x9cNxe2x80x9d denotes a total number of electrodes). Hence, those input lines are respectively connected to switches (145), each of which is provided for a group of thirty-two electrodes.
In the above, print information (i.e., pulse signal) is supplied to each group of thirty-two electrodes in a serial manner by which the electrodes are being driven at sequentially different timings. This causes unwanted deviations in print positions of dots as shown in FIG. 38C.
In addition, the aforementioned fine pitch electrode unit is designed to drive the electrodes in response to analog signals. For this reason, it is difficult to adjust relationships between actual printing densities and gradation values corresponding to print data. In the case of color printing, it is difficult to adjust print positions among different colors of ink. That is the aforementioned electro-coagulation printer needs a mechanical installation accuracy to be strictly maintained among mechanical parts such that the electrodes are strictly aligned in a prescribed direction while maintaining a constant gap being formed between the electrodes and rotation drum. In other words, there is a drawback in that the conventional electro-coagulation printer cannot perform high-quality printing without strictly maintaining the mechanical installation accuracy among the mechanical parts.
It is an object of the invention to provide a method and an apparatus for electro-coagulation printing in which printing is performed with a high quality and at a high speed.
It is another object of the invention to provide an electrode control unit which is suited to the electro-coagulation printing method and apparatus.
A printing method of this invention for an electro-coagulation printer is realized by a print data reception step, a gradation data creation step, a parallel conversion step, a gradation value hold step, a parallel drive control step and an electrode drive step. Herein, the gradation data creation step creates gradation data representing gradation values for one line of pixels on the basis of the print data received by the print data reception step. The parallel conversion step receives the gradation data which are serially transferred thereto to parallel data corresponding to the gradation values with respect to one line of electrodes, which are aligned in proximity to a rotation drum having a conductive ink film on its surface. After the gradation value hold step completely holds one line of the gradation values, the parallel drive control step simultaneously outputs the gradation values in parallel to the electrode drive step to drive the electrodes respectively. Driving the electrodes, the conductive ink film is partially coagulated to form ink dots on the surface of the rotation drum, so that the ink dots are transferred onto a paper.
In the above, the gradation value can be configured using an arbitrary number of bits. If the gradation value is represented by eight bits, there are provided 256 steps of gradation. Incidentally, the gradation value can be configured by a single bit, in which digit 0 designates a blank (or white dot) while digit 1 designates a black dot. In the parallel conversion step, the gradation values serially input are output onto a parallel bus including lines for the electrodes respectively, so that one line of the gradation values are converted to parallel data. The printer waits for the timing when the gradation value hold step completely holds one line of the gradation values. Then, the parallel drive control step simultaneously outputs the gradation values in parallel so that the electrode drive step simultaneously drives the electrodes. Thus, it is possible to secure linearity in printing in an alignment direction of the electrodes. The electrode drive step performs drive controls independently on the electrodes based on the gradation values. So, it is possible to independently correct the timings of driving the electrodes with ease. Therefore, it is possible to cope with positional deviations that occur in installation positions of the electrodes. That is, those deviations can be absorbed by changing destinations of the gradation values with respect to the electrodes respectively or by correcting output timings of the gradation values. Inputting the gradation values in parallel, the electrode drive step independently drives the electrodes based on the gradation values. Hence, it is possible to correct the gradation values independently with respect to the electrodes with ease. That is, it is possible to easily correct the electrodes being driven in accordance with relationships between gradation values and actual printing densities.
An electro-coagulation printer of this invention is basically constructed using electrodes which are aligned in proximity to a rotation drum having an conductive ink film on its surface. Hence, the electrodes are electrified to partially coagulate the conductive ink film to form ink dots on the surface of the rotation drum, so that the ink dots are transferred onto a paper. The electro-coagulation printer is characterized by providing an interface, a data processing section, an output timing control section, a pulse generation section and an electrode drive section. Herein, the data processing section creates gradation data corresponding to a collection of gradation values for pixels on the basis of print data received by the interface. The output timing control section controls timings of outputting the gradation values in parallel with respect to one line of the electrodes independently. The pulse generation section generates pulse signals in response to the gradation values which are output by the timings being independently controlled by the output timing control section. Using the pulse signals, the electrode drive section drives the electrodes in parallel.
In the above, when print data are input to the interface, the data processing section specifies gradation values for pixels respectively on the basis of the print data. The output timing control section controls output timings for one line of gradation values independently. Herein, the gradation values are output with delays which are determined in consideration of installation positions of the electrodes. The pulse generation section converts the gradation values independently input thereto to pulse signals. Using the pulse signals, the electrode drive section drives the electrodes respectively, so that the electrodes are independently driven in parallel. Thus, it is possible to improve linearity in printing. If the electrodes are uniformly aligned in a straight line, they are simultaneously driven. If the electrodes are aligned with small positional deviations in installation, they are driven based on the pulse signals at specific timings which are designated in response to the positional deviations. Thus, it is possible to secure linearity in high-speed printing in an alignment direction of the electrodes by absorbing differences among the installation positions of the electrodes. In addition, signal processing is adequately performed to absorb positional shifts of electrodes which are respectively aligned for different colors in color printing or differences of gaps measured between the electrodes and rotation drum in printing with shading. So, it is possible to improve quality in printing. In addition, the pulse generation section converts the gradation values to pulse signals respectively. So, it is possible to easily perform corrections on the gradation values or pulse signals in accordance with relationships between the gradation values and actual printing densities. Those corrections can be performed with linearity being maintained in printing.